This invention relates in general to an apparatus for inflicting electric injury upon land shellfish such as snails, slugs and the like and other living things harmful in agriculture.
Heretofore, in order to protect the crops and the like from living things harmful in agriculture represented by land shellfish like snails, there was a method of enveloping an area to be protected entirely with a wall and applying a coating on the wall surface with a chemical substance for repelling such harmful living things, but these methods were not effective because of the cost of equipment therefor being high or the aspect of efficacy being questionable. Also, a method for protecting such area electrically from harmful living things was likewasie proposed. In this so-called electric fence method the area to be protected is encircled with an electric fence comprising a pair of conductors and a high-voltage (for example, merely a voltage of 110 V for commercial use) is applied to such conductors. Because of this high-voltage current, the greater part of harmful living things are either killed by an electric shock or at least deprived of their ability to move into the area involved. In this sense, the method of using such electric fence is effective, but is not reliable and rugged and, because of the high-voltage utilized, the danger to men and beasts is great.
An approach to keeping snails or the like out the a protected area is disclosed in Swiss Pat. No. 443,773, granted Feb. 15, 1968. In this patent, a pair of horizontally spaced insulating conductors are laid on the ground and pulses of voltage are applied thereto in a manner which will kill or shock the snails as they bridge the conductors. This means of protecting an area from shellfish and the like has the disadvantage that when the snails are not killed, they are undesirably still free to roam in the area involved to cause a nuisance, even though they may not be able to enter a given protected area.
It is an object of the present invention to provide means for protecting a given area against the intrusion of shellfish or the like without danger to human beings and wherein the shellfish are not killed but are rather trapped within a defined area.
Accordingly, this invention has for its object the elimination of one or more of the above-mentioned disadvantages of the electric fence.